U.S. patent number 7,908,436 [Application Number 12/110,193] was granted by the patent office on 2011-03-15 for deduplication of data on disk devices using low-latency random read memory.
This patent grant is currently assigned to NetApp, Inc.. Invention is credited to Garth Goodson, Kiran Srinivasan, Kaladhar Voruganti.
United States Patent |
7,908,436 |
Srinivasan , et al. |
March 15, 2011 |
Deduplication of data on disk devices using low-latency random read
memory
Abstract
Deduplication of data using a low-latency random read memory
(LLRRM) is described herein. Upon receiving a block, if a matching
block stored on a disk device is found, the received block is
deduplicated by producing an index to the address location of the
matching block. In some embodiments, a matching block having a
predetermined threshold number of associated indexes that reference
the matching block is transferred to LLRRM, the threshold number
being one or greater. Associated indexes may be modified to reflect
the new address location in LLRRM. Deduplication may be performed
using a mapping mechanism containing mappings of deduplicated
blocks to matching blocks, the mappings being used for performing
read requests. Deduplication described herein may reduce read
latency as LLRRM has relatively low latency in performing random
read requests relative to disk devices.
Inventors: |
Srinivasan; Kiran (Cupertino,
CA), Goodson; Garth (Fremont, CA), Voruganti;
Kaladhar (San Jose, CA) |
Assignee: |
NetApp, Inc. (Sunnyvale,
CA)
|
Family
ID: |
43708228 |
Appl.
No.: |
12/110,193 |
Filed: |
April 25, 2008 |
Current U.S.
Class: |
711/114;
711/103 |
Current CPC
Class: |
G06F
3/0641 (20130101); G06F 3/0622 (20130101); G06F
16/13 (20190101); G06F 3/0689 (20130101) |
Current International
Class: |
G06F
12/02 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Eran Gal and Sivan Toledo, Algorithms and Data Structures for Flash
Memories, ACM Computing Surveys (CSUR) Archive, Jun. 2005, pp.
138-163, vol. 37, Issue 2, Publisher ACM, New York City, NY, USA.
cited by other .
U.S. Appl. No. 12/110,122, filed Apr. 25, 2008, Srinivasan, et al.
cited by other.
|
Primary Examiner: Nguyen; Than
Attorney, Agent or Firm: Stattler-Suh PC
Claims
We claim:
1. A storage system for deduplicating blocks of data, the storage
system comprising: a set of one or more disk devices for storing a
plurality of blocks; a set of one or more low-latency random read
memory (LLRRM) devices for storing a plurality of blocks, an LLRRM
device having lower latency in performing random read requests
relative to a disk device; and a deduplication layer configured
for: receiving a set of blocks; for each received block,
determining whether the received block matches a block stored on a
disk device; and upon determining that a matching stored block is
found in a disk device, deduplicating the received block by:
transferring the matching stored block from an original address
location on a disk device to a new address location in an LLRRM
device; and producing an index to the matching stored block, the
index comprising the new address location of the matching stored
block in the LLRRM device.
2. The storage system of claim 1, wherein a matching stored block
is transferred to an LLRRM device upon the first instance of the
stored block matching a received block.
3. The storage system of claim 1, wherein a received block matches
a stored block when the blocks have the same data content or have a
high probability of having the same content.
4. The storage system of claim 1, further comprising: comparison
mechanism for storing metadata entries for a plurality of stored
blocks, each metadata entry comprising metadata for a stored block
and being indexed in the comparison mechanism by a content
identifier that represents the data contents of the stored block,
wherein the deduplication layer is configured for determining
whether a received block matches a stored block using the
comparison mechanism.
5. The storage system of claim 4, wherein the deduplication layer
is configured for determining whether a received block matches a
stored block by determining a content identifier for the received
block and determining whether a matching content identifier is
found in the comparison mechanism, wherein two blocks having the
same content identifier have a high probability of having the same
data content.
6. The storage system of claim 4, wherein a metadata entry for a
stored block comprises a reference count indicating the number of
indexes that reference the stored block and a set of pointers to
the indexes, a pointer being used to modify an index to reflect the
new address location when a stored block is transferred to an LLRRM
device.
7. The storage system of claim 1, further comprising: a mapping
mechanism for storing mappings of deduplicated received blocks to
corresponding matching stored blocks, wherein the deduplication
layer is configured for producing indexes to matching stored blocks
in the mapping mechanism, wherein: the mapping mechanism comprises
a set of inodes or a metadata structure; and the mapping mechanism
is used for performing a subsequent read request for deduplicated
received blocks, wherein the read request comprises a read of one
or more matching stored blocks on an LLRRM device.
8. The storage system of claim 7, wherein: a received block
comprises a block to be written to a disk device using a write log
comprising the data of the block and an assigned address location
for the block on the disk device; and the deduplication layer is
further configured for deduplicating a received block by deleting
the data of the block and the assigned address location for the
block in the write log.
9. The storage system of claim 7, wherein: the received blocks
comprise blocks stored on a disk device; and the deduplication
layer is further configured for deduplicating a received block by
deleting the received block stored on the disk device.
10. The storage system of claim 1, further comprising: a driver
selector layer for receiving an access request that specifies an
address location and sending the received request to a disk device
driver or an LLRRM driver depending on the value of the address
location.
11. The storage system of claim 1, wherein an LLRRM device
comprises a flash memory, Magnetic Random Access Memory (MRAM), or
Phase Change RAM (PRAM) device.
12. A storage system for deduplicating blocks of data, the storage
system comprising: a set of one or more disk devices for storing a
plurality of blocks; a set of one or more low-latency random read
memory (LLRRM) devices for storing a plurality of blocks, an LLRRM
device having lower latency in performing random read requests
relative to a disk device; and a deduplication layer configured
for: receiving a set of blocks; for each received block,
determining whether the received block matches a block stored on a
disk device; and upon determining that a matching stored block is
found in a disk device, deduplicating the received block by:
determining whether a number of associated indexes referencing the
matching stored block equals a predetermined threshold number, the
threshold number being two or greater; upon determining that the
threshold number of associated indexes reference the matching
stored block, transferring the matching stored block from an
original address location on a disk device to a new address
location in an LLRRM device; and producing an index to the matching
stored block, the index comprising the new address location of the
matching stored block in the LLRRM device.
13. The storage system of claim 12, wherein the number of
associated indexes indicate a number of received blocks that are
deduplicated using the matching stored block.
14. The storage system of claim 12, wherein a received block
matches a stored block when the blocks have the same data content
or have a high probability of having the same content.
15. The storage system of claim 12, further comprising: comparison
mechanism for storing metadata entries for a plurality of stored
blocks, each metadata entry comprising metadata for a stored block
and being indexed in the comparison mechanism by a content
identifier that represents the data contents of the stored block,
wherein the deduplication layer is configured for determining
whether a received block matches a stored block using the
comparison mechanism.
16. The storage system of claim 15, wherein the deduplication layer
is configured for determining whether a received block matches a
stored block by determining a content identifier for the received
block and determining whether a matching content identifier is
found in the comparison mechanism, wherein two blocks having the
same content identifier have a high probability of having the same
data content.
17. The storage system of claim 15, wherein a metadata entry for a
stored block comprises a reference count indicating the number of
associated indexes that reference the stored block and a set of
pointers to the associated indexes, a pointer being used to modify
an associated index to reflect the new address location when a
stored block is transferred to an LLRRM device.
18. The storage system of claim 12, wherein an LLRRM device
comprises a flash memory, Magnetic Random Access Memory (MRAM), or
Phase Change RAM (PRAM) device.
19. A storage system for deduplicating blocks of data based on a
predetermined threshold number (THN) of sequential blocks, the
storage system comprising: a set of one or more disk devices for
storing a plurality of blocks, each disk device comprising a set of
tracks for storing blocks; a set of one or more low-latency random
read memory (LLRRM) devices for storing a plurality of blocks, an
LLRRM device having lower latency in performing random read
requests relative to a disk device; and a deduplication layer
configured for: receiving a set of blocks; determining that a
series of THN or more received blocks (THN series) matches a
sequence of THN or more stored blocks (THN sequence), a series of
blocks comprising a set of consecutive blocks and a sequence of
blocks comprising a series of blocks stored on a same track of a
disk device, THN having a value of 2 or greater; deduplicating the
blocks of the THN series using the matching THN sequence; for at
least one received block, determining that the received block
matches a block stored on a disk device; and deduplicating the
received block by: transferring the matching stored block from an
original address location on a disk device to a new address
location in an LLRRM device; and producing an index to the matching
stored block, the index comprising the new address location of the
matching stored block in the LLRRM device.
20. The storage system of claim 19, wherein a sequence of blocks
comprises blocks having consecutive address locations.
21. The storage system of claim 19, wherein a matching stored block
is transferred to an LLRRM device upon the first instance of the
stored block matching a received block.
22. The storage system of claim 19, wherein a received block
matches a stored block when the blocks have the same data content
or have a high probability of having the same content.
23. The storage system of claim 19, wherein an LLRRM device
comprises a flash memory, Magnetic Random Access Memory (MRAM), or
Phase Change RAM (PRAM) device.
Description
RELATED APPLICATIONS
This application is related to U.S. patent application Ser. No.
12/110,122, entitled "Deduplication of Data on Disk Devices Based
on a Threshold Number of Sequential Blocks," by Kiran Srinivasan,
et al., filed herewith, and incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to storage systems, and particularly,
to deduplication of data on disk devices using low-latency random
read memory.
BACKGROUND OF THE INVENTION
A storage system is a processing system adapted to store and
retrieve information/data on storage devices (such as disks). The
storage system includes a storage operating system that implements
a file system to logically organize the information as a
hierarchical structure of directories and files on the storage
devices. Each file may comprise a set of data blocks, whereas each
directory may be implemented as a specially-formatted file in which
information about other files and directories are stored.
The storage operating system generally refers to the
computer-executable code operable on a storage system that manages
data access and access requests (read or write requests requiring
input/output operations) and may implement file system semantics in
implementations involving storage systems. In this sense, the Data
ONTAP.RTM. storage operating system, available from Network
Appliance, Inc. of Sunnyvale, Calif., which implements a Write
Anywhere File Layout (WAFL.RTM.) file system, is an example of such
a storage operating system implemented as a microkernel within an
overall protocol stack and associated storage. The storage
operating system can also be implemented as an application program
operating over a general-purpose operating system, such as
UNIX.RTM. or Windows.RTM., or as a general-purpose operating system
with configurable functionality, which is configured for storage
applications as described herein.
A storage system's storage is typically implemented as one or more
storage volumes that comprise physical storage devices, defining an
overall logical arrangement of storage space. Available storage
system implementations can serve a large number of discrete
volumes. A storage volume is "loaded" in the storage system by
copying the logical organization of the volume's files, data, and
directories, into the storage system's memory. Once a volume has
been loaded in memory, the volume may be "mounted" by one or more
users, applications, devices, and the like, that are permitted to
access its contents and navigate its namespace.
A storage system may be configured to allow server systems to
access its contents, for example, to read or write data to the
storage system. A server system may execute an application that
"connects" to the storage system over a computer network, such as a
shared local area network (LAN), wide area network (WAN), or
virtual private network (VPN) implemented over a public network
such as the Internet. The application executing on the server
system may send an access request (read or write request) to the
storage system for accessing particular data stored on the storage
system.
The storage system may implement deduplication methods when storing
data on the storage devices. Deduplication methods may be used to
remove redundant data and to ensure that only a single instance of
the same data is stored on the storage devices. Rather than storing
multiple copies of the same data on the storage devices, a single
instance of the data is typically stored and referenced/indexed
multiple times. Since redundant data is removed, deduplication of
data typically saves storage space.
Deduplication of data, however, may also cause longer read
latencies when reading data that has been deduplicated (e.g., as
compared to performing sequential read accesses on a file that has
not been deduplicated). For example, when a file to be written to
the storage devices is received, any blocks of the received file
that match any blocks currently stored in the storage devices are
typically considered redundant blocks and are deduplicated (i.e.,
are deleted from or not stored to the storage devices and a
reference/index to the address location of the matching stored
blocks is produced in their place). Any non-redundant blocks in the
received file are written to the storage devices. When a read
request for the received file is later received, the storage system
performs the read request by retrieving the stored non-redundant
blocks and, for each redundant block, uses the reference/index
produced for the redundant block to seek and retrieve its matching
stored block.
However, when the storage devices comprise disk devices, the
matching stored blocks may be written on particular tracks of a
platter of the disk device, whereas the non-redundant blocks of the
received file are typically written on different tracks of the disk
device. When reading blocks from the same track, a read/write head
of the disk device typically exhibits low latency times as it may
quickly retrieve the blocks sequentially from the same track. When
reading blocks from different tracks, however, a read/write head of
the disk device incurs significant seek times each time it
repositions onto a different track to retrieve a block of data.
Since deduplication of data is typically performed on a
single-block basis (whereby each individual block found to be
redundant is deduplicated), later reading of the received file may
incur significant read latency if the read/write head frequently
seeks and retrieves single blocks stored on different tracks. For
example, later reading of the received file may comprise retrieving
non-redundant blocks on a first track, seeking and retrieving a
single matching stored block on a second track, then seeking and
retrieving non-redundant blocks on the first track, then seeking
and retrieving a single matching stored block on the second track,
etc.
As such, conventional use of deduplication on a single-block basis
on a disk device may later cause significant read latency as the
read/write head of the disk device repositions back and forth
between different tracks to seek and retrieve single matching
blocks. As such, there is a need for a method and apparatus for
utilizing deduplication of data on disk devices that mitigates the
later read latency of the data.
SUMMARY OF THE INVENTION
A method and apparatus for deduplication of data using low-latency
random read memory (referred to herein as "LLRRM") is described
herein. In some embodiments, an LLRRM (e.g., flash memory, etc.)
comprises a device having lower latency in performing random read
requests relative to disk devices. In these embodiments,
deduplication may be performed by receiving a series of one or more
blocks and, for each received block, determining whether the
received block matches (in data content) a block stored on a
storage device. If a matching stored block is found to exist for a
received block, the received block may be deduplicated using the
matching stored block, whereby the matching stored block is
transferred from the storage device to an LLRRM. In some
embodiments, the storage device comprises a disk device. As such,
deduplication using LLRRM may reduce the later read latency of a
file or set of blocks.
If a matching block is not found to exist, a received block is not
deduplicated and is stored to a storage device. If a matching
stored block is found to exist, a received block is considered
redundant and is deduplicated. Deduplication of the received block
may be performed by deleting from or not storing the received block
to a storage device and producing an index to the address location
of the matching stored block. In some embodiments, a number of
indexes ("associated indexes") referencing the matching stored
block is also checked to determine whether to transfer the matching
stored block to LLRRM. The number of associated indexes may
indicate the number of redundant blocks ("associated deduplicated
blocks") that are deduplicated using the matching stored block. In
some embodiments, a reference count represents the number of
associated indexes or associated deduplicated blocks.
In some embodiments, a matching stored block having one associated
index (or associated deduplicated block) is transferred to LLRRM
for storage. In some embodiments, a matching stored block having a
predetermined threshold number (THN) of associated indexes (or
associated deduplicated blocks) is transferred to LLRRM for
storage, the threshold number being one or greater. When
transferred to LLRRM from a storage device, the matching stored
block is assigned a new address location in LLRRM. Any associated
indexes for any associated deduplicated blocks may be modified to
reflect the new address location of the matching stored block in
LLRRM. As such, deduplication of the received redundant block may
be performed by producing an index to the new address location of
the matching stored block in LLRRM.
In some embodiments, deduplication is performed using a
block-comparison mechanism and a mapping mechanism. It is
determined if a received block matches a stored block by querying
the block-comparison mechanism. The block-comparison mechanism may
comprise metadata entries of currently stored blocks. The received
blocks may also be processed to create new metadata entries in the
block-comparison mechanism. Based on the results of the query to
the block-comparison mechanism, a received block may be
deduplicated. If so, an index to the matching stored block is
produced in the mapping mechanism which is used to record mappings
of deduplicated redundant blocks to their corresponding matching
stored blocks (whether stored in LLRRM or on a storage device). The
mapping mechanism may be used to perform later read requests
received for deduplicated blocks.
In some embodiments, deduplication methods are used that leverage
the particular characteristics and advantages of LLRRM over disk
devices. In some embodiments, an LLRRM comprises a device having
lower latency in performing random read requests relative to disk
devices. In some embodiments, LLRRM may comprise non-volatile,
rewritable computer memory having relatively low latency in
performing random read requests compared with disk devices.
Examples of LLRRM devices include flash memory, Magnetic Random
Access Memory (MRAM), Phase Change RAM (PRAM), or the like. In some
embodiments, LLRRM does not comprise a set of tracks for storing
data blocks (as do disk devices). Thus, seek operations to read
blocks stored on different tracks are not needed when performing
read operations on LLRRM (and thereby seek latencies are not
incurred in LLRRM). As such, when matching blocks are later read
from LLRRM, read latency may be mitigated.
The deduplication methods using LLRRM described herein may be used
in conjunction with other deduplication methods for disk devices
(such as a deduplication method that provides efficient sequential
accesses to disk devices). In some embodiments, the deduplication
methods using LLRRM described herein are used in combination with a
deduplication method for disk devices based on a threshold number
(THN) of sequential blocks, which is described in U.S. patent
application Ser. No. 12/110,122, entitled "Deduplication of Data on
Disk Devices Based on a Threshold Number of Sequential Blocks," by
Kiran Srinivasan, et al., filed herewith, and incorporated herein
by reference. In these embodiments, matching blocks (used for
deduplicating received blocks) that occur in a sequence are may be
stored on a disk device while also reducing read latency. For
matching blocks that may not be efficiently stored on disk devices,
the matching blocks may be stored to LLRRM.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features are set forth in the appended claims. However,
for purpose of explanation, several embodiments of the invention
are set forth in the following figures.
FIG. 1 is a schematic block diagram of an exemplary storage system
environment in which some embodiments operate;
FIG. 2 is a schematic block diagram of an exemplary storage system
that may be employed in the storage system environment of FIG.
1;
FIG. 3 is a schematic block diagram of an exemplary storage
operating system that may be implemented by the storage system in
FIG. 2;
FIG. 4 is a conceptual diagram of storage-side layers of the
storage operating system;
FIG. 5 is a conceptual diagram of storage-side layers of the
storage operating system comprising a de-staging layer;
FIG. 6 is a conceptual representation of a disk platter of a disk
device;
FIG. 7 shows a conceptual diagram of stored file X and received
file Y;
FIG. 8 shows a conceptual diagram of the blocks that comprise the
received file Y after deduplication of redundant blocks;
FIG. 9 shows a conceptual diagram of the storage and reading of
file Y;
FIG. 10 shows a conceptual diagram of an inode associated with file
Y;
FIG. 11 shows a conceptual diagram of an exemplary block-comparison
mechanism comprising a metadata structure;
FIG. 12 shows a conceptual diagram of an exemplary mapping
mechanism comprising a metadata structure;
FIGS. 13A-B are flowcharts of a method for deduplication of data
using LLRRM;
FIG. 14 is a flowchart of a method for producing new metadata
entries in the block-comparison mechanism; and
FIG. 15 is a flowchart of a method for deduplication of data using
a THN sequence method in combination with an LLRRM method.
DETAILED DESCRIPTION
In the following description, numerous details are set forth for
purpose of explanation. However, one of ordinary skill in the art
will realize that the embodiments described herein may be practiced
without the use of these specific details. In other instances,
well-known structures and devices are shown in block diagram form
in order not to obscure the description with unnecessary
detail.
The description that follows is divided into six sections. Section
I describes a storage system environment in which some embodiments
operate. Section II describes deduplication of data on disk
devices. Section III describes deduplication of data using LLRRM.
Section IV describes block-comparison and mapping mechanisms used
for deduplication of data using LLRRM. Section V describes methods
for implementing deduplication of data using LLRRM. Section VI
describes using the deduplication methods for using LLRRM described
herein in combination with a deduplication method for disk devices
based on a threshold number (THN) of sequential blocks.
I. Storage System Environment
FIG. 1 is a schematic block diagram of an exemplary storage system
environment 100 in which some embodiments operate. The environment
100 comprises a one or more server systems 110 and a storage system
120 (comprising a set of one or more storage devices 125 and a set
of one or more low-latency random read memory (LLRRM) devices 135)
that are connected via a connection system 150. The connection
system 150 may comprise a network, such as a Local Area Network
(LAN), Wide Area Network (WAN), metropolitan area network (MAN),
the Internet, or any other type of network or communication system
between computer systems.
A server system 110 may comprise a computer system that utilizes
services of the storage system 120 to store and manage data in the
storage devices 125 of the storage system 120. A server system 110
may execute one or more applications 115 that submit read/write
requests for reading/writing data on the storage devices 125 of the
storage system 120. In some embodiments, the storage system 120 may
receive read/write requests from two or more applications 115
(executing on one or more server systems 110) simultaneously. The
two or more applications 115 may be accessing different sets of
storage devices 125 or volumes of the storage system 120.
Interaction between a server system 110 and the storage system 120
can enable the provision of storage services. That is, server
system 110 may request the services of the storage system 120
(e.g., through read or write requests), and the storage system 120
may perform the requests and return the results of the services
requested by the server system 110, by exchanging packets over the
connection system 150. The server system 110 may issue access
requests (e.g., read or write requests) by issuing packets using
file-based access protocols, such as the Common Internet File
System (CIFS) protocol or Network File System (NFS) protocol, over
the Transmission Control Protocol/Internet Protocol (TCP/IP) when
accessing data in the form of files and directories. Alternatively,
the server system 110 may issue access requests by issuing packets
using block-based access protocols, such as the Fibre Channel
Protocol (FCP), or Internet Small Computer System Interface (iSCSI)
Storage Area Network (SAN) access, when accessing data in the form
of blocks.
The storage system 120 may comprise a computer system that stores
data in a set of one or more storage devices 125. A storage device
125 may comprise a writable storage device media, such as disk
devices, video tape, optical, DVD, magnetic tape, and any other
similar media adapted to store information (including data and
parity information). In some embodiments, a storage device 125
comprises a disk device (described in detail below). In other
embodiments, the storage device 125 may comprise any other type of
storage device. In some embodiments, the storage system 120 also
stores data in a set of one or more LLRRM devices 135.
The storage system 120 may implement a file system to logically
organize the data as a hierarchical structure of directories and
files on the storage devices 125 and LLRRM devices 135. Each file
may be implemented as a set of blocks configured to store data,
whereas each directory may be implemented as a specially-formatted
file in which information about other files and directories are
stored. A block of a file may comprise a fixed-sized amount of data
that comprises the smallest amount of storage space that may be
accessed (read or written) on a storage device 125. The block may
vary widely in data size (e.g., 1 byte, 4-kilobytes (KB), 8 KB,
etc.).
In some embodiments, a file system specific for LLRRM is
implemented on an LLRRM 135, such as Journalling Flash File System
(JFFS), JFFS2, Yet Another Flash File System (YAFFS), etc. As known
in the art, the LLRRM 135 may implement a sub-system for performing
various input/output operations (such as transferring/storing data
onto the LLRRM 135 and for later accessing data on the LLRRM 135).
The sub-system may comprise a device driver, file system, and other
software layers for performing the various input/output
operations.
The LLRRM device 135 may comprise a separate (stand-alone) LLRRM
135 or may be integrated as part of a storage device 125 (such as a
hybrid drive comprising an LLRRM and a magnetic storage combined in
a single device). As discussed below in relation to FIG. 2, an
LLRRM device may also reside in the storage system's internal
architecture and be connected with the system bus (e.g., as an
LLRRM module on a card). Some embodiments herein may utilize the
LLRRM in a similar manner, regardless of the configuration or
location of the LLRRM, so that the LLRRM and storage device(s) 125
operate together in a way that is transparent to applications
accessing data stored on the storage system 120.
In some embodiments, an LLRRM device 135 may comprise rewritable
computer memory having relatively low latency in performing random
read requests compared with disk devices. Examples of LLRRM devices
include flash memory, Magnetic Random Access Memory (MRAM), Phase
Change RAM (PRAM), or the like. The LLRRM device 135 may comprise a
non-volatile, rewritable computer memory (i.e., a computer memory
that does not require power to maintain information stored in the
computer memory and may be electrically erased and reprogrammed).
In some embodiments, the non-volatile characteristic of LLRRM is
utilized by transferring matching blocks stored on a disk device
125 to an LLRRM device 135 for storage. In these embodiments, after
being transferred from the storage device 125 and stored to the
LLRRM, a matching stored block may optionally be deleted from the
storage device 125 on which it was originally stored. In further
embodiments, any subsequent read requests of transferred matching
stored blocks are performed by retrieving the matching stored
blocks from LLRRM rather than a disk device.
In some embodiments, LLRRM does not comprise a set of tracks for
storing data blocks (as do disk devices). Thus, seek operations and
time penalties for random reading of blocks stored on different
tracks are not incurred when performing read operations on LLRRM.
In some embodiments, this characteristic of LLRRM is utilized by
storing matching blocks on an LLRRM device 135 (rather than a disk
device) for performing later read operations on the matching
blocks, thus mitigating read latency.
FIG. 2 is a schematic block diagram of an exemplary storage system
120 that may be employed in the storage system environment of FIG.
1. Those skilled in the art will understand that the embodiments
described herein may apply to any type of special-purpose computer
(e.g., storage system) or general-purpose computer, including a
standalone computer, embodied or not embodied as a storage system.
To that end, storage system 120 can be broadly, and alternatively,
referred to as a computer system. Moreover, the teachings of the
embodiments described herein can be adapted to a variety of storage
system architectures including, but not limited to, a
network-attached storage environment, a storage area network and
disk assembly directly-attached to a server computer. The term
"storage system" should, therefore, be taken broadly to include
such arrangements.
The storage system 120 comprises a network adapter 210, a processor
220, a memory 240, a non-volatile random access memory (NVRAM) 245,
and a storage adapter 250 interconnected by a system bus 260. In
some embodiments, the storage system 120 further comprises an LLRRM
device 135 that resides in the storage system's internal
architecture and is connected with the system bus 260. For example,
the LLRRM device 135 may be an LLRRM module on a Peripheral
Component Interconnect (PCI) or PCI eXtended (PCI-X) card that is
connected with the system bus 260.
The network adapter 210 comprises the mechanical, electrical and
signaling circuitry needed to connect the storage system 120 to a
server system 110 over a computer network 150. The storage system
may include one or more network adapters. Each network adapter 210
has a unique IP address and may provide one or more data access
ports for server systems 110 to access the storage system 120
(where the network adapter accepts read/write access requests from
the server systems 110 in the form of data packets).
The memory 240 comprises storage locations that are addressable by
the processor 220 and adapters for storing software program code
and data. The memory 240 may comprise a form of random access
memory (RAM) that is generally cleared by a power cycle or other
reboot operation (e.g., it is a "volatile" memory). In other
embodiments, however, the memory 240 may comprise a non-volatile
form of memory that does not require power to maintain information.
The processor 220 and adapters may, in turn, comprise processing
elements and/or logic circuitry configured to execute the software
code and manipulate the data stored in the memory 240.
The storage system 120 may also include a NVRAM 245 that may be
employed as a backup memory that ensures that the storage system
120 does not "lose" received information, e.g., CIFS and NFS
requests, in the event of a system shutdown or other unforeseen
problem. The NVRAM 245 is typically a large-volume solid-state
memory array (RAM) having either a back-up battery, or other
built-in last-state-retention capabilities (e.g. an LLRRM), that
holds the last state of the memory in the event of any power loss
to the array. Therefore, even if an access request stored in memory
240 is lost or erased (e.g., due to a temporary power outage) it
still may be recovered from the NVRAM 245.
The processor 220 executes a storage operating system application
300 of the storage system 120 that functionally organizes the
storage system by, inter alia, invoking storage operations in
support of a file service implemented by the storage system. In
some embodiments, the storage operating system 300 comprises a
plurality of software layers (including a deduplication layer 275)
that are executed by the processor 220. In some embodiments, the
deduplication layer 275 is implemented to deduplicate data using
LLRRM 135. Portions of the storage operating system 300 are
typically resident in memory 240. It will be apparent to those
skilled in the art, however, that other processing and memory
means, including various computer readable media, may be used for
storing and executing program instructions pertaining to the
storage operating system 300.
In some embodiments, a metadata structure 290 is also resident in
memory 240. In other embodiments, the metadata structure 290 may
also be resident in NVRAM 245, or stored on a storage device 125.
As discussed below, in some embodiments, the metadata structure 290
is produced and used by the deduplication layer 275 to store
metadata for stored blocks and is used to determine whether
received blocks match any stored blocks. In these embodiments, the
metadata structure 290 is sometimes referred to as a
block-comparison mechanism. In other embodiments, the metadata
structure 290 is also used by the deduplication layer 275 to record
mappings of deduplicated redundant blocks to their corresponding
matching stored blocks. In these embodiments, the metadata
structure 290 is sometimes also referred to as a mapping
mechanism.
In some embodiments, the metadata structure 290 may be stored on
LLRRM 135. The deduplication layer 275 accesses various data in the
metadata structure 290 which may be stored in various locations in
the metadata structure 290. As such, random reads of data on the
metadata structure 290 may be used by the deduplication layer 275.
Since LLRRM provides persistent non-volatile storage as well as low
latency for random reads, the metadata structure 290 may be stored
on LLRRM 135 in some embodiments.
The storage adapter 250 cooperates with the storage operating
system 300 executing on the storage system 120 to access data
requested by the server system 110. The data may be stored on the
storage devices 125 and LLRRM devices 135 that are attached, via
the storage adapter 250, to the storage system 120 or other node of
a storage system as defined herein. The storage adapter 250
includes input/output (I/O) interface circuitry that couples to the
storage devices 125 and LLRRM devices 135 over an I/O interconnect
arrangement, such as a conventional high-performance, Fibre Channel
serial link topology. In response to an access request received
from a server system 110, data may be retrieved by the storage
adapter 250 and, if necessary, processed by the processor 220 (or
the adapter 250 itself) prior to being forwarded over the system
bus 260 to the network adapter 210, where the data may be formatted
into a packet and returned to the server system 110.
In an illustrative embodiment, the storage devices 125 may comprise
disk devices that are arranged into a plurality of volumes, each
having a file system associated therewith. In some embodiments, the
storage devices 125 comprise disk devices that are configured into
a plurality of RAID (redundant array of independent disks) groups
whereby multiple storage devices 125 are combined into a single
logical unit (i.e., RAID group). In a typical RAID group, storage
devices 125 of the group share or replicate data among the disks
which may increase data reliability or performance. The storage
devices 125 of a RAID group are configured so that some disks store
striped data and at least one disk stores separate parity for the
data, in accordance with a preferred RAID-4 configuration. However,
other configurations (e.g. RAID-5 having distributed parity across
stripes, RAID-DP, etc.) are also contemplated. A single volume
typically comprises a plurality of storage devices 125 and may be
embodied as a plurality of RAID groups.
The organization of a storage operating system 300 for the
exemplary storage system 120 is now described briefly. However, it
is expressly contemplated that the principles of the embodiments
described herein can be implemented using a variety of alternative
storage operating system architectures. As discussed above, the
term "storage operating system" as used herein with respect to a
storage system generally refers to the computer-executable code
operable on a storage system that implements file system semantics
(such as the above-referenced WAFL.RTM.) and manages data access.
In this sense, Data ONTAP.RTM. software is an example of such a
storage operating system implemented as a microkernel. The storage
operating system can also be implemented as an application program
operating over a general-purpose operating system, such as
UNIX.RTM. or Windows.RTM., or as a general-purpose operating system
with configurable functionality.
As shown in FIG. 3, the storage operating system 300 comprises a
set of software layers that form an integrated protocol software
stack. The protocol stack provides data paths 360 for server
systems 110 to access data stored on the storage system 120 using
data-access protocols. The protocol stack includes a media access
layer 310 of network drivers (e.g., an Ethernet driver). The media
access layer 310 interfaces with network communication and protocol
layers, such as the Internet Protocol (IP) layer 320 and the
transport layer 330 (e.g., TCP/UDP protocol). The IP layer 320 may
be used to provide one or more data access ports for server systems
110 to access the storage system 120. In some embodiments, the IP
layer 320 layer provides a dedicated private port for each of one
or more remote-file access protocols implemented by the storage
system 120.
A data-access protocol layer 340 provides multi-protocol data
access and, for example, may include file-based access protocols,
such as the Hypertext Transfer Protocol (HTTP) protocol, the NFS
protocol, the CIFS protocol, and so forth. The storage operating
system 300 may include support for other protocols, such as
block-based access protocols. Such protocols may include, but are
not limited to, the direct access file system (DAFS) protocol, the
web-based distributed authoring and versioning (WebDAV) protocol,
the Fibre Channel Protocol (FCP), the Internet small computer
system interface (iSCSI) protocol, and so forth.
The storage operating system 300 may manage the storage devices 125
and LLRRM 135 using storage-side layers 370. As shown in FIG. 4,
the storage-side layers 370 may include a storage layer 380 (that
implements a storage protocol, such as a RAID protocol), driver
selector layer 382, and a device driver layer 385 (comprising a
disk driver 390 and an LLRRM driver 395). Bridging the storage-side
layers 370 with the network and protocol layers is a file system
layer 350 of the storage operating system 300. In an illustrative
embodiment, the file system layer 350 implements a file system
having an on-disk format representation that is block-based using
inodes to describe the files.
The file system layer 350 may determine an address space for the
set of storage devices 125 and set of LLRRM devices 135 of the
storage system 120. The address space may comprise a total range of
address locations for storing data blocks in the set of storage
devices 125 and the set of LLRRM devices 135, wherein each data
block in a storage device 125 or an LLRRM device 135 is assigned a
unique address location within the address space. In some
embodiments, the file system layer 350 may further determine,
within the total range of address locations, a disk sub-range of
address locations for storing data blocks in the set of storage
devices 125 and a memory sub-range of address locations for storing
data blocks in the set of LLRRM devices 135.
For example, the address space may comprise a total range of
logical block numbers (LBNs) 0 through N for storing data blocks in
the set of storage devices 125 and the set of LLRRM devices 135,
wherein each data block in a storage device 125 or an LLRRM device
135 is assigned a unique LBN. The file system layer 350 may further
determine within the total range of LBNs (0 through N), a disk
sub-range of LBNs (0 through M) for storing data blocks in a set of
disk devices 125 and a memory sub-range of LBNs (M+1 through N) for
storing data blocks in the set of LLRRM devices 135. As used
herein, "LBN Dn" may indicate an LBN value within the disk
sub-range of LBNs and "LBN Fn" may indicate an LBN value within the
memory sub-range of LBNs. As such, for example, a block having LBN
D1 indicates the block is stored on the set of disk devices 125 and
a block having LBN F1 indicates the block is stored on the set of
LLRRM devices 135.
The file system layer 350 also assigns, for each file, a unique
inode number and an associated inode. An inode may comprise a data
structure used to store metadata information about the file (such
as name of the file, when the file was produced or last modified,
ownership of the file, access permission for the file, size of the
file, etc.). Each inode may also contain information regarding the
block locations of the file. In some embodiments, the block
locations are indicated by LBNs assigned for each block of the
file. The file system 350 may store and maintain an inode file that
contains and indexes (by inode number) the inodes of the various
files.
In response to receiving a file-access request (containing an
external file handle) from a server system 110, the file system 350
generates operations to perform the request (such as storing data
to or loading/retrieving data from the storage devices 125 or LLRRM
135). The external file handle in the access request typically
identifies a file or directory requested by the server system 110.
Specifically, the file handle may specify a generation number,
inode number and volume number corresponding to the accessed data.
If the information is not resident in the storage system's memory
240, the file system layer 350 indexes into the inode file using
the received inode number to access the appropriate inode entry for
the identified file and retrieve file location information (e.g.,
LBN) from the inode. The file system layer 350 then passes the
access request and requested LBN to the appropriate driver (for
example, an encapsulation of SCSI implemented on a fibre channel
interconnection) of the device driver layer 385. In these
embodiments, the device driver layer 385 that implements a device
control protocol (such as small computer system interface (SCSI),
integrated drive electronics (IDE), etc.).
In some embodiments, the file system layer 350 passes the access
request and specified LBN to the driver selector layer 382 which
then passes the request and the LBN to the disk driver 390 or the
LLRRM driver 395 of the device driver layer 385. In these
embodiments, based on the value of the received address location
(e.g., LBN), the driver selector layer 382 determines which driver
in the device driver layer 385 to send the received access request
and address location for processing. In these embodiments, the
driver selector layer 382 sends received requests having address
locations within the disk sub-range of address locations (e.g.,
LBNs) to the disk device driver 390 and sends received requests
having address locations within the memory sub-range of address
locations (e.g., LBNs) to the LLRRM driver 395 for processing. As
such, the driver selector layer 382 may be used to perform write or
read requests on the set of storage devices 125 or the set of LLRRM
135 as needed by some embodiments described herein.
Using the received LBNs, the device driver layer 385 accesses the
appropriate blocks from the storage devices 125 or the LLRRM
devices 135 and loads requested data in memory 240 for processing
by the storage system 120. In some embodiments, if the LBN is
within the disk sub-range of LBNs, the disk driver 390 accesses the
appropriate blocks from the storage devices 125. If the LBN is
within the memory sub-range of LBNs, the LLRRM driver 395 accesses
the appropriate blocks from the LLRRM devices 135. Upon successful
completion of the request, the storage system (and storage
operating system) returns a response (e.g., a conventional
acknowledgement packet defined by the CIFS specification) to the
server system 110 over the network 150.
It should be noted that the software "path" 360 through the storage
operating system layers described above needed to perform data
storage access for the requests received at the storage system may
alternatively be implemented in hardware or a combination of
hardware and software. That is, in an alternative embodiment, the
storage access request path 360 may be implemented as logic
circuitry embodied within a field programmable gate array (FPGA) or
an application specific integrated circuit (ASIC). This type of
hardware implementation may increase the performance of the file
service provided by storage system 120 in response to a file system
request packet issued by server system 110. Moreover, in a further
embodiment, the processing elements of network and storage adapters
210 and 250 may be configured to offload some or all of the packet
processing and storage access operations, respectively, from
processor 220 to thereby increase the performance of the data
access service provided by the storage system 120.
In some embodiments, the storage operating system 300 also
comprises a deduplication layer 275 that operates in conjunction
with the other software layers and file system of the storage
operating system 300 to deduplicate data stored on the storage
system 120 as described herein. For example, in some embodiments,
the deduplication layer 275 may reside between the file system
layer 350 and the storage layer 380 of the storage operating system
300 (as shown in FIGS. 3 and 4). In other embodiments, the
deduplication layer 275 may reside near other layers of the storage
operating system 300.
In some embodiments, the storage-side layers 370 also include a
de-staging layer 375 (as shown in FIG. 5). For example, in some
embodiments, the de-staging layer 375 may reside between the file
system layer 350 and the deduplication layer 275 of the storage
operating system 300 (as shown in FIGS. 3 and 5). In other
embodiments, the de-staging layer 375 may reside near other layers
of the storage operating system 300. The de-staging layer 375 may
be implemented in some storage systems 125 to perform received
write requests for files in two stages. In a first stage, write
requests received by the file system layer 350 are sent to the
de-staging layer 375, a write request containing blocks of data to
be written. The de-staging layer 375 produces a write log for each
received write request, a write log containing the blocks of data
to be written. The write logs 295 may be stored, for example, to
the NVRAM 245 (as shown in FIG. 2). In a second stage, at
predetermined time intervals (referred to as consistency points),
accumulated write logs 295 (e.g., in the NVRAM 245) are sent to the
storage layer 380 which then writes the blocks of data in the write
logs to a storage device 125.
Embodiments described herein may be applied to a storage system 120
that is implemented with or with out a de-staging layer 375. In
some embodiments, the deduplication layer 275 is used in
conjunction with the de-staging layer 375. In these embodiments,
the deduplication layer 275 may process the write logs accumulated
during the first stage that are awaiting the next consistency point
to be written to a storage device 125. During this time, the
deduplication layer 275 may process the blocks in the accumulated
write logs for possible deduplication before the blocks are written
to the storage devices 125. In other embodiments, the deduplication
layer 275 is used without use of a de-staging layer 375. In these
embodiments, the deduplication layer 275 may receive write requests
from the file system 350 and process blocks of the write requests
for deduplication as they are received.
Note that when a write log for a write request for a file is
produced in the first stage, the file system layer 350 may assign
LBNs for each block in the file to be written, the assigned LBN of
a block indicating the location on a storage device 125 where the
block will be written to at the next consistency point. Also, the
file system layer 350 may assign an inode number and an inode for
the file. As such, each write log may comprise blocks of data to be
written, the locations (LBNs) of where the blocks are to be
written, and an inode number assigned to the file. When a write log
for a write request for a file is produced in the first stage, the
file system layer 350 may also store LBNs for the blocks of the
file in its assigned inode.
In other embodiments where the deduplication layer 275 is used
without the de-staging layer 375, the deduplication layer 275 may
receive write requests for files from the file system 350, whereby
the file system layer 350 may assign LBNs for each block in the
file to be written. Also, the file system layer 350 may assign an
inode number and an inode for the file and store the assigned LBN
for the blocks of the file in its assigned inode.
In some embodiments, the deduplication layer 275 may be
pre-included in storage operating system 300 software. In other
embodiments, the deduplication layer 275 may comprise an external
auxiliary plug-in type software module that works with the storage
operating system 300 to enhance its functions. As such, the
deduplication layer 275 may be imposed upon an existing storage
operating system 300 and file system 350 to provide deduplication
of data as described herein. In further embodiments, the
deduplication layer 275 may comprise an external auxiliary plug-in
type software module that works with pre-existing deduplication
software to enhance functions of the deduplication software as
described herein.
II. Deduplication of Data on Disk Devices
The storage system 120 may implement deduplication methods when
storing data on the storage devices 125. Deduplication methods may
be used to remove redundant data and ensure that only a single
instance of the same data is stored on the storage devices. Rather
than storing multiple copies of the same data on the storage
devices, a single instance of the data is typically stored and
referenced/indexed multiple times. Deduplication of data may be
applied at any level, for example, across a single storage device
125 or volume (where redundant data within the single storage
device 125 or volume are removed), across multiple storage devices
125 or volumes (where redundant data within multiple storage
devices 125 or volumes are removed), across the entire storage
system 120 (where redundant data within the storage system 120 are
removed), across multiple storage systems 120 (where redundant data
within the multiple storage systems 120 are removed), and so forth.
Since redundant data is removed, deduplication of data typically
saves storage space. Deduplication of data, however, may also cause
longer read latencies when reading data that has been deduplicated
on a disk device.
As known in the art, a disk device comprises a plurality of stacked
platters, each platter having a read/write head that retrieves and
writes data to the platter. FIG. 6 shows a conceptual
representation of a disk platter 605 that comprises a plurality of
tracks 610 (shown as concentric circles), each track being divided
into a plurality of sectors/blocks 615 (shown as segments of the
concentric circles). As used herein, a "block" may comprise any
size of data (e.g., 1 byte, 4 KB, 8 KB, etc.). Each block that is
stored in the storage system 120 is typically assigned a unique
logical block number (LBN) by the file system 350. In the
embodiments described below, the locations of blocks are indicated
by LBNs. However, in other embodiments, the storage locations of
blocks are indicated by another type of number (other than
LBN).
As used herein, blocks 615 on a disk platter 605 are accessed
"sequentially" when they are accessed from the same track 610 in
order (i.e., accessed one after another along the same track). When
reading blocks sequentially from the same track, the read/write
head of the disk device typically exhibits low latency times. As
used herein, blocks 615 on a disk platter 605 are accessed
"randomly" when they are accessed from different tracks 610. When
reading blocks from different tracks, the read/write head of the
disk device may incur significant latency time each time it
repositions onto a different track to retrieve a block of data. As
used herein, the read/write head performs a "seek" when moving to a
different track which incurs a "seek time" latency.
Read latency may be incurred when using conventional "single-block"
deduplication methods for disk devices. For example, when a file to
be written to the storage devices is received, a comparison is
performed to determine whether any of the blocks of the received
file match any blocks currently stored in the storage devices. As
used herein, a "received" file comprises a "received" set of blocks
that are processed for deduplication. The received blocks are
compared to "currently stored" blocks of "currently stored" files
that are presently stored on disk devices 125 of the storage system
120. Note that in some situations (e.g., in offline processing),
received blocks may also be currently stored on the storage system
120. In these embodiments, currently stored blocks may be compared
to other currently stored blocks to determine if any of the
currently stored blocks may be deduplicated.
A received block that matches a currently stored block is referred
to as a "redundant block," whereas the corresponding currently
stored block is referred to as a "matching stored block." A
received block that does not match any currently stored blocks is
referred to as a "non-redundant block." A block may be considered
to "match" another block when both blocks have the same content or
there is a high probability that both blocks have the same
content.
Deduplication of a redundant block may comprise deleting from or
not storing the redundant block to the storage devices and,
producing in their place, an index to the address location of the
corresponding matching stored blocks (the index being produced, for
example, in the inode for the received file). Any received
non-redundant blocks are not deduplicated and are written to the
storage devices. For each written non-redundant block, an index to
the address location of the non-redundant block where the block was
stored may also be produced in the inode for the received file.
When a read request for the received file is later received, the
storage system may perform the read request by using the inode to
index and retrieve the stored non-redundant blocks and, for each
redundant block, the corresponding matching stored block.
When the storage devices 125 comprise disk devices, the matching
stored blocks may be written on particular tracks 610 of the disk
device, whereas the non-redundant blocks of the received file are
typically written on different tracks of the disk device.
Deduplication of data on disk devices is typically performed on a
single-block basis, whereby each individual block found to be
redundant is deduplicated. As such, later reading of the received
file (using the indexes to the matching stored blocks and
non-redundant blocks in the inode for the file) may incur
significant read latency if the read/write head frequently seeks
and retrieves single blocks stored on different tracks. For
example, later reading of the received file may comprise retrieving
non-redundant blocks on a first track, seeking and retrieving a
single matching stored block on a second track, then seeking and
retrieving non-redundant blocks on the first track, then seeking
and retrieving a single matching stored block on the second track,
etc. As such, conventional "single-block" deduplication methods may
result in a later read operation that incurs significant seek
latencies.
III. Deduplication of Data Using LLRRM
In some embodiments, deduplication of a received series of blocks
is performed using LLRRM. As used herein, a "series" of blocks
indicates a set of consecutive/adjacent blocks in a predetermined
order. As used herein, blocks of a series are numbered by
consecutive "block-series numbers" (BSNs) that indicate the
ordering of the blocks in the series. BSNs may be used below in
relation to a series of received blocks. Note however, that a
series of received blocks may also have associated LBNs assigned by
the file system layer 350.
If a matching block is not found to exist, a received block is not
deduplicated and is stored to a storage device. If a matching
stored block is found to exist, a received block is considered
redundant and is deduplicated. Deduplication of the received block
may be performed by deleting from or not storing the received block
to a storage device and producing an index to the address location
of the matching stored block in a mapping mechanism for the
received block. In some embodiments, the number of indexes
(referred to as "associated indexes") that reference the matching
stored block is also checked to determine whether to transfer the
matching stored block to LLRRM. The number of associated indexes
for a matching stored block may indicate the number of redundant
blocks (referred to as "associated deduplicated blocks") that are
deduplicated using the matching stored block. In some embodiments,
a reference count for a matching stored block represents the number
of associated indexes or associated deduplicated blocks of the
matching stored block.
In some embodiments, a matching stored block having a predetermined
threshold number (THN) of associated indexes (or associated
deduplicated blocks) are transferred to LLRRM for storage, the
threshold number being one or greater. In some embodiments, the
matching stored block is transferred to LLRRM upon the first
instance of the stored block matching a received block (i.e., where
THN is set to equal one). In other embodiments, the matching stored
block is transferred to LLRRM upon two or more instances of the
stored block matching a received block (i.e., where THN is set to
equal two or greater). When transferred to LLRRM from a storage
device, the matching stored block is assigned a new address
location in LLRRM. As such, deduplication of the received redundant
block may further include producing an index to the new address
location of the matching stored block in LLRRM. Also, any
prior-produced associated indexes in the mapping mechanism for any
prior associated deduplicated blocks may be modified to reflect the
new address location of the matching stored block in LLRRM.
In some embodiments, if the matching stored block does not have the
threshold number (THN) of associated indexes (or associated
deduplicated blocks), the matching stored block is not transferred
to LLRRM and the index for the received block is produced using the
current address location of the matching stored block. If the
matching stored block has a number of associated indexes (or
associated deduplicated blocks) that is greater than THN, this
indicates that the matching stored block has already been
transferred to LLRRM. Thus the current address location of the
matching stored block used to produce the index for the received
block is the address location of the matching stored block in
LLRRM. In contrast, if the matching stored block has a number of
associated indexes (or associated deduplicated blocks) that is less
than THN, this indicates that the matching stored block has not
already been transferred to LLRRM and is still stored on a disk
device. Thus the current address location of the matching stored
block used to produce the index for the received block is the
original address location of the matching stored block on the disk
device.
In some embodiments, deduplication is performed using a
block-comparison mechanism and a mapping mechanism. It is
determined if a received block matches a stored block by querying
the block-comparison mechanism. The block-comparison mechanism may
comprise metadata entries of currently stored blocks. The received
blocks may also be processed to create new metadata entries in the
block-comparison mechanism. Based on the results of the query to
the block-comparison mechanism, a received block may be
deduplicated. If so, an index to the matching stored block is
produced in the mapping mechanism which is used to record mappings
of deduplicated redundant blocks to their corresponding matching
stored blocks on a storage device or in LLRRM. The mapping
mechanism may be used to perform later read requests received for
deduplicated blocks.
In some embodiments, deduplication methods are used that leverage
the particular characteristics and advantages of LLRRM over disk
devices. LLRRM may comprise non-volatile, rewritable computer
memory having relatively low latency in performing random read
requests compared with disk devices. In some embodiments, LLRRM
does not comprise a set of tracks for storing data blocks (as do
disk devices). Thus, seek operations to read blocks stored on
different tracks are not needed when performing read operations on
LLRRM (and thereby seek latencies are not incurred in LLRRM). As
such, when matching blocks are later read from LLRRM, read latency
may be mitigated.
In some embodiments, the deduplication methods described herein are
performed by the deduplication layer 275 of the storage operating
system 300. In some embodiments, received blocks are processed for
deduplication prior to being written to a storage device 125
(referred to as online processing). In these embodiments, the
deduplication layer 275 may receive blocks to be written and
determine deduplication prior to any of the received blocks being
written to a storage device 125. In online processing, storage
space may be saved immediately and unnecessary write operations to
storage devices 125 are avoided. In other embodiments, blocks are
processed for deduplication after being written to a storage device
125 (referred to as offline processing). In these embodiments, the
deduplication layer 275 may process blocks currently stored to the
storage devices 125 to determine whether deduplication of the
stored blocks is needed. In offline processing, if deduplication is
performed on blocks found to be redundant, the redundant blocks may
be deleted from the storage devices 125.
FIGS. 7-10 are exemplary conceptual diagrams illustrating
deduplication using LLRRM in accordance with some embodiments. FIG.
7 shows a conceptual diagram of a first file 710 ("file X")
comprising a plurality of blocks 715 and a second file 750 ("file
Y") comprising a plurality of blocks 755. In the example of FIG. 7,
file X comprises a currently stored file comprising a series of 8
blocks 715 having LBNs (X, X+1, X+2 . . . X+7), whereby X is the
LBN of the first block in the series. In the example of FIG. 7,
file Y comprises a received file that is to be processed for
deduplication. File Y comprises a series of 9 blocks 755 numbered
by BSNs (Y, Y+1, Y+2 . . . Y+8) that indicate the ordering of the
blocks in the series, whereby Y is the BSN of the first block in
the series.
In the example of FIG. 7, block BSN (Y+3) of file Y matches block
LBN (X+3) 720 of file X and block BSN (Y+5) of file Y matches block
LBN (X+5) 720 of file X. As such, two redundant blocks 760 in
received file Y 750 and are to be deduplicated using two matching
blocks 720 in stored file X 710. When deduplicating a redundant
block 760, the redundant block 760 is deleted from or not stored to
the storage devices 125 and an index to the address locations
(e.g., LBN X+3 and LBN X+5) of the corresponding matching block 720
is produced in their place.
FIG. 8 shows a conceptual diagram of the blocks that will comprise
the received file Y after deduplication of the redundant blocks 760
is performed. As shown in FIG. 8, the received file Y will comprise
non-redundant blocks BSN (Y) through BSN (Y+2), matching block LBN
(X+3), non-redundant block BSN (Y+4), matching block LBN (X+5), and
non-redundant blocks BSN (Y+6) through BSN (Y+8).
In the example of FIG. 7, it is assumed that each matching block
720 has a threshold number (THN) of associated indexes and thus are
assigned new address locations in LLRRM and are transferred to
LLRRM for storage. As such, FIG. 9 shows a conceptual diagram of
the storage of the blocks of file Y and the operations of a read
request for file Y after the matching blocks 720 have been
transferred to LLRRM 135. In the example of FIG. 9, non-redundant
blocks BSN (Y) through BSN (Y+2), BSN (Y+4), and BSN (Y+6) through
BSN (Y+8) of file Y are stored on a first track 950 of a disk
device (and have assigned LBNs (Y) through LBN (Y+6),
respectively). The matching block LBN (X+3) has a new address
location (e.g., LBN F1) and matching block LBN (X+5) has a new
address location (LBN F2) in LLRRM 135.
FIG. 10 shows a conceptual diagram of an inode 1005 associated with
file Y that stores the LBNs of each block of file Y (in accordance
with FIG. 9). The LBNs of the blocks of file Y are stored in the
inode 1005 in the particular order needed to properly read the
blocks of file Y. When a later read request is received for file Y,
the storage operating system 300 would retrieve the associated
inode 1005 and retrieve the blocks at the LBNs stored in the
associated inode 1005, the blocks being retrieved in the particular
order specified in the associated inode 1005.
In the example of FIG. 9, when a read request for file Y is later
received, the read request is performed according to the associated
inode 1005 of file Y. As such, the read request would be performed
as follows: sequential read 960 on blocks having LBNs (Y) through
LBN (Y+2) on the first track 950, random read 970 on the LLRRM 135
to retrieve LBN (F1), read block LBN (Y+3) on the first track 950,
random read 970 on the LLRRM 135 to retrieve LBN (F2), and
sequential read 960 on blocks having LBNs (Y+6) through LBN (Y+8)
on the first track 950.
Under typical deduplication methods, the matching blocks 720 of
file X would be stored on a second track of the disk device. As
such, upon later reading of file Y, matching blocks LBN (X+3) and
LBN (X+5) would be retrieved from the second track of the disk
device, thus incurring seeks times for each matching block that is
retrieved. Thus, the above example illustrates how read latency of
the received blocks of file Y may be mitigated using LLRRM 135
since random reads 970 are then performed on LLRRM 135 rather than
seek operations performed across different tracks on a disk
device.
Iv. Block-Comparison and Mapping Mechanisms
A. Introduction
In some embodiments, the deduplication layer 275 performs
deduplication of blocks using a block-comparison mechanism and a
mapping mechanism. The deduplication layer 275 receives a series of
blocks for processing. The received blocks may be contained in a
file (for file-based access) or not contained in a file (for
block-based access). The received blocks may have not yet been
written to a disk device (in online processing), whereby any
received blocks that are found to be redundant and deduplicated are
not subsequently written to a disk device. The received blocks may
have already been written to a disk device (in offline processing),
whereby any received blocks that are found to be redundant and
deduplicated may be deleted from the disk device.
The deduplication layer 275 determines whether a received block
matches a currently stored block by querying the block-comparison
mechanism. In some embodiments, the block-comparison mechanism
comprises the metadata structure 290 which contains a plurality of
metadata entries representing a plurality of currently stored
blocks. The deduplication layer 275 also processes the received
blocks to create new metadata entries for the received blocks in
the metadata structure 290. In some embodiments, a metadata entry
representing a stored block includes a reference count indicating
the number of indexes (associated indexes) that reference the
stored block. As such, the reference count may indicate how many
blocks (associated deduplicated blocks) are deduplicated using the
stored block. In some embodiments, the metadata structure 290 is
resident in memory 240 or NVRAM 245, stored on a storage device
125, and/or stored on an LLRRM device 135.
Based on the results of the query to the block-comparison
mechanism, it is determined whether a matching stored block has
been found. If so, the received block is deduplicated using the
matching stored block by deleting from or not storing the received
block to the storage devices and producing a reference/index to the
address location of the matching stored block. The deduplication
layer 275 may then increase the reference count in the metadata
entry for the matching stored block in the metadata structure 290.
The deduplication layer 275 then determines whether the reference
count (i.e., the number of associated indexes or associated blocks)
is equal to the predetermined threshold number (THN).
If the reference count is equal to the predetermined threshold
number, the matching stored block is transferred to LLRRM for
storage, the matching stored block having a new address location in
LLRRM. Each associated index of the matching block is then modified
in the mapping mechanism to reflect the new address location of the
matching stored block in LLRRM. As such, an index for the received
block is produced in the mapping mechanism using the new address
location of the matching stored block in LLRRM. Also, any
prior-produced associated indexes in the mapping mechanism for any
prior associated deduplicated blocks are also modified to reflect
the new address location of the matching stored block in LLRRM. If
the reference count is not equal to the predetermined threshold
number, the matching stored block is not transferred to LLRRM and
an index for the received block is produced in the mapping
mechanism using the current address location of the matching stored
block (whether on a disk device or LLRRM).
Also, in offline processing (where the received block may have
already been written to a disk device), deduplication of the
received block may further comprise deleting the received block
from the disk device. In online processing (where the received
block have not yet been written to a disk device), deduplication of
the redundant received block may comprise not subsequently storing
the received block to a disk device.
The mapping mechanism is used to record mappings of deduplicated
redundant blocks to their corresponding matching stored blocks
whether in LLRRM or on a storage device. The mapping mechanism may
be used by the storage operating system 300 to perform later read
requests received for the received blocks. In some embodiments, for
file-based access, the mapping mechanism comprises the set of
inodes associated with the files of the storage system 120. In some
embodiments, for block-based access, the mapping mechanism
comprises the metadata structure 290 which contains mapping entries
of deduplicated blocks.
As such, the deduplication layer 275 uses the block-comparison
mechanism for performing two general functions in relation to a
received series of blocks. Function 1 (the comparison function) is
to determine whether a received block matches a currently stored
block, whereby the received block may then be deduplicated. Note
that in the comparison function, although the received block of
received blocks have assigned LBNs, the BSNs (rather than the
assigned LBNs) of the received blocks are used in the comparison
function. Function 2 (the entry function) is to process the
received series of blocks to produce new metadata entries in the
block-comparison mechanism for possible use in deduplicating
subsequently received blocks. In the entry function, the assigned
LBNs of the received blocks may be used since the entries in the
block-comparison mechanism are based on address locations.
B. Metadata Structure
FIG. 11 shows a conceptual diagram of an exemplary block-comparison
mechanism comprising a metadata structure 290. The metadata
structure 290 contains metadata for "stored blocks" that are
currently stored on a storage device 125 or LLRRM 135 or are
awaiting to be stored on a storage device 125 or LLRRM 135 (and
have assigned LBNs). In the example of FIG. 11, the metadata
structure 290 comprises a plurality of metadata entries 1101, a
metadata entry representing a corresponding stored block. The
metadata structure 290 may implement an indexing system to organize
the metadata entries 1101 to provide efficient entry lookups in the
metadata structure 290. For example, the entries 1101 may be
indexed using checksum or hashing algorithms (discussed below).
In some embodiments, a metadata entry 1101 for a corresponding
stored block may comprise fields for a content identifier 1105, an
address location on a disk device 1120, an address location on an
LLRRM device 1125, a reference count 1130, a set of zero or more
pointers 1135 to zero or more associated indexes, or any
combination of these. The metadata structure 290 may contain a
metadata entry 1101 for each stored block. In the example of FIG.
11, the THN value is set to equal two.
The content identifier 1105 represents the data contents of the
blocks of the corresponding stored block and is produced using a
content identifier operation/algorithm on the data contents of the
stored block. The content identifier 1105 may be used as an index
for the corresponding entry. The type of content identifier 1105
used may be such that two blocks having the same content identifier
have a high probability of also having the same data content.
In some embodiments, the content identifier of a block is
determined using a checksum operation/algorithm that produces a
checksum value representing the data contents of the block, the
checksum value comprising the content identifier. For example, a
checksum value may comprise a 128 or 256 bit number that represents
the data contents of a block. As known in the art, when two blocks
have the same checksum value, there is a high probability that the
two blocks have the same data content, whereby only in rare
instances is this not true. In other embodiments, the content
identifier is determined by applying a hashing operation/algorithm
to the checksum value that produces a hash value representing the
data contents of the block, the hash value comprising the content
identifier. In further embodiments, the content identifier is
determined using other operations/algorithms.
The address location on a disk device 1120 indicates the original
address location (e.g., LBN D1, etc.) of the corresponding stored
block on a disk device where the block is/was originally stored.
The address location on LLRRM device 1125 indicates the new address
location (e.g., LBN F1, etc.) of the corresponding stored block in
LLRRM (if the block has been transferred to LLRRM). For example,
for file-based access, an address location 1120 or 1125 may
comprise a file identifier and the LBN of the stored block. For
block-based access, the address location 1120 or 1125 may comprise
the LBN of the stored block. Note that in the example of FIG. 11,
THN is set to equal two. Thus, entries 1101 with a reference count
1130 of two or greater have an address location in LLRRM 1125
(since only these entries represent matching stored blocks that
have been transferred to LLRRM).
The reference count 1130 may indicate how many blocks index the
corresponding stored block. In some embodiments, the reference
count 1130 comprises a number of indexes (associated indexes) that
reference the corresponding stored block. In other embodiments, the
reference count 1130 comprises the number of redundant blocks
(associated deduplicated blocks) that match (in data content) the
corresponding stored block and are deduplicated using the
corresponding stored block.
In some embodiments, each associated index of a stored block is
stored in a mapping mechanism, each associated index having a
unique address location (e.g., LBN) where the index is stored
within the mapping mechanism. Note that the associated index may
comprise the address location of the corresponding stored block
(e.g., the LBN of the stored block on a disk device 1120 or an
LLRRM device 1125). In some embodiments, the address location of
the corresponding stored block may be modified if it is transferred
to LLRRM. As such, a pointer 1135 to each associated index may be
produced in and stored in a metadata entry 1101 for a stored block.
In some embodiments, a pointer 1135 to an associated index
comprises an address location (e.g., LBN) of the associated index
within the mapping mechanism. For example, for a reference count
equal to 3 (indicating 3 associated indexes), three pointers 1135
are produced (e.g., P1, P2, P3) and stored in the entry 1101, one
pointer for each associated index. Upon the corresponding stored
block being transferred to LLRRM, the deduplication layer 275 may
use the pointers 1135 to locate the associated indexes and modify
the associated indexes using the new address location of the
corresponding stored block in LLRRM.
C. Comparison Function of the Block-Comparison Mechanism
In some embodiments, when the deduplication layer 275 receives a
series of blocks for processing, the deduplication layer 275 may
first perform a comparison function using the metadata structure
290 to determine whether any of the received blocks may be
deduplicated. The deduplication layer 275 may process each received
block by determining a content identifier that represents the data
contents of the received block. The content identifier for the
received block may be produced using the steps used to produce the
content identifiers 1105 in the metadata structure 290. For
example, the content identifier of the received block may be
determined by applying a checksum operation to the block, and
applying a hashing operation to the checksum to produce a hashing
value that comprises the content identifier for the block.
The deduplication layer 275 then queries the metadata structure 290
using the content identifier for the received block. If a matching
content identifier 1105 is found in the metadata structure 290,
this indicates a matching entry 1101 has been found that represents
a matching stored block. As discussed above, the type of content
identifier is used such that two blocks having the same content
identifier have a high probability of also having the same data
content (for example, when using a checksum or hash value). As
such, there is a high probability that the matching stored block
represented by the matching entry has the same data content as the
received block. As an optional step, the deduplication layer 275
may confirm this is true by comparing the contents of the received
block with the matching block. When a matching content identifier
1105 and matching entry 1101 is found in the metadata structure
290, the received block is deduplicated using the corresponding
matching stored block.
The comparison function is performed for each received block in the
series of received blocks. After processing of all received blocks,
any blocks that are not considered redundant and deduplicated are
non-redundant blocks that are to be stored to a storage device 125.
The non-redundant blocks are then processed according to the entry
function of the deduplication layer 275.
D. Entry Function of the Block-Comparison Mechanism
Received blocks that are not deduplicated are referred to as the
set of non-deduplicated blocks. The entry function of the
deduplication layer 275 processes the non-deduplicated blocks to
produce new entries 1101 in the block-comparison mechanism (e.g.,
metadata structure 290) for possible use in deduplicating
subsequently received blocks. The non-deduplicated blocks have
address locations (e.g., LBNs) assigned by the file system layer
350 indicating where the non-deduplicated blocks are to be stored
on a storage device 125.
For each non-deduplicated block in the set, the deduplication layer
275 produces a metadata entry 1101 having particular metadata
regarding the non-deduplicated block in the metadata structure 290.
The deduplication layer 275 may do so by producing a content
identifier for the non-deduplicated block and using the content
identifier as an index to store the metadata entry 1101 in the
metadata structure 290. For example, the content identifier may
comprise a checksum or hash value.
When initially producing the metadata entry 1101 for the
non-deduplicated block, the metadata entry 1101 may comprise the
content identifier 1105, the address location on a disk device 1120
(e.g., the LBN assigned to the non-deduplicated block), and the
reference count 1130 (which is initially set to zero). The other
metadata fields (e.g., address location on an LLRRM device 1125, a
set of zero or more pointers 1135) may initially have null values
and may subsequently be modified by the deduplication layer 275 if
later received blocks match the non-deduplicated block. The
deduplication layer 275 may repeat the process for each
non-deduplicated block in the set.
E. Mapping Mechanism
When the deduplication layer 275 deduplicates a redundant received
block, it produces an index in the mapping mechanism to the
matching block in place of the redundant received block. The index
may comprise, for example, the address locations (e.g. LBNs) on a
disk device or LLRRM of the matching block. As such, the mapping
mechanism is used to record mappings of deduplicated redundant
blocks to their corresponding matching stored blocks. The mapping
mechanism may be used by the storage operating system 300 to
perform later read requests received for deduplicated redundant
blocks.
In some embodiments, for file-based access (using, for example,
CIFS or NFS protocols), the mapping mechanism comprises the set of
inodes associated with the files of the storage system 120, the
inodes being maintained by the file system layer 350. In these
embodiments, when blocks of a file are deduplicated, the
deduplication layer 275 produces indexes (LBNs) to the matching
blocks in the inode of the file (as discussed above in relation to
FIG. 10). In other embodiments, the deduplication layer 275 may
send a request to the file system layer 350 that maintains the
inodes to produce the appropriate indexes in the appropriate inode.
Later read requests received for a file having deduplicated
redundant blocks may then be performed by the storage operating
system 300 by using the inode for the file and the LBNs contained
in the inode (as per usual). In these embodiments, a pointer 1135
to an associated index of a matching block comprises an address
location of the associated index in the inode for the file having
the deduplicated redundant block.
In some embodiments, for block-based access (for example, in SAN or
iSCSI access), the mapping mechanism comprises the metadata
structure 290 which further contains mapping entries of
deduplicated blocks. In other embodiments, the mapping mechanism
comprises a data structure that is separate from the metadata
structure 290. FIG. 12 shows a conceptual diagram of an exemplary
mapping mechanism comprising a metadata structure 290. In these
embodiments, in addition to the plurality of metadata entries 1101,
the metadata structure 290 further comprises a plurality of mapping
entries 1201, one mapping entry 1201 for each deduplicated
block.
A mapping entry 1201 may comprise an assigned location 1205 (e.g.,
an LBN assigned by the file system layer 350) for a deduplicated
block and an index 1210 (e.g., address location on a disk device or
LLRRM) to a corresponding matching stored block. For example, a
mapping entry 1201 may comprise the assigned LBN 1205 for a
deduplicated block and an LBN on a disk device (Dn) 1210 or an LBN
in LLRRM (Fn) 1210 for the corresponding matching stored block. In
these embodiments, a pointer 1135 to an associated index of a
matching block comprises an address location of the index 1210 in
the corresponding mapping entry 1201 in the metadata structure
290.
Later read requests received for deduplicated blocks may then be
performed by the storage operating system 300 by using the metadata
structure 290. Each read request will specify address locations
(e.g., LBNs) of deduplicated blocks to be read. The metadata
structure 290 may then be used to map the LBNs of the deduplicated
blocks (received in the read request) to LBNs of the corresponding
matching blocks (whereby the data of the corresponding matching
blocks are retrieved using the LBNs).
F. De-Staging Layer
In some embodiments, the deduplication layer 275 may be used in
conjunction with a de-staging layer 375. In these embodiments, the
deduplication layer 275 may process the write logs accumulated
during a first stage that are awaiting the next consistency point
to be written to a storage device 125. During this time, the
deduplication layer 275 may process the blocks in the accumulated
write logs for possible deduplication before the blocks are written
to the storage devices 125. When the deduplication layer 275 is
used with a de-staging layer 375, additional steps may be used when
deduplicating blocks.
As discussed above, a write log for a write request for a file
produced in the first stage may comprise data of the blocks to be
written, the locations (LBNs) of where the blocks are to be
written, and an assigned inode number. When a write log for a write
request for a file is produced in the first stage, the file system
layer 350 may also store LBNs for each block of the file in its
assigned inode.
As such, when redundant blocks are deduplicated according to the
embodiments herein, the write logs containing the deduplicated
blocks may be modified to reflect the deduplication. For example,
modifications to a write log containing deduplicated blocks may
include deleting the deduplicated blocks from the write log and
removing the address locations (e.g., LBNs) of the deduplicated
blocks from the write log. These additional steps may be performed
since the deduplicated blocks should not be written to the storage
devices 125. As such, when the write log is later sent to the
storage layer 380, the write log only contains non-deduplicated
blocks which are written to a storage device 125 in the second
stage.
G. Threshold Number
As described above, in some embodiments, a matching stored block
having a predetermined threshold number (THN) of associated indexes
(or associated deduplicated blocks) are transferred to LLRRM for
storage, the threshold number being one or greater. In some
embodiments, the matching stored block is transferred to LLRRM upon
the first instance of the stored block matching a received block
(i.e., where THN is set to equal one). In other embodiments, the
matching stored block is transferred to LLRRM upon having two or
more instances of the stored block matching a received block (i.e.,
where THN is set to equal two or greater).
As such, the threshold number may be varied to control the number
of matching blocks that are stored to LLRRM. For example, if the
storage size amount of LLRRM is relatively low, the threshold
number may be set to a relatively high number to reduce the number
of matching blocks that are stored to LLRRM. Or if the storage size
amount of LLRRM is relatively high, the threshold number may be set
to a relatively low number to increase the number of matching
blocks that are stored to LLRRM.
Further, if the amount of LLRRM is limited, the threshold number
may also be varied to transfer only those matching blocks to LLRRM
that have a certain expected frequency level for future reads (the
expected frequency level for future reads being reflected by the
number of associated indexes or associated deduplicated blocks).
For example, if a matching block has a relatively high number of
associated indexes or associated deduplicated blocks, the matching
block has a relatively higher expected frequency level for future
reads. As such, if it is determined that only matching blocks
having a relatively high frequency level of expected future reads
are to be transferred to LLRRM, the threshold number may be set to
a relatively high number.
In some embodiments, the deduplication layer 275 comprises a
parameter interface 280 (as shown in FIG. 2) that receives the
threshold number as a parameter to dynamically change the threshold
number. In some embodiments, the parameter is received from a user
through the parameter interface 280 which comprises a user
interface (such as, a graphical user interface or command line
interface). In other embodiments, the parameter may be received
from a program through the parameter interface 280 which comprises
a program interface, such as, an application program interface
(API). The received parameter may dynamically change the threshold
number used by the deduplication layer 275 without requiring the
software code of the deduplication layer 275 to be modified.
V. Methods for Deduplication Using LLRRM
FIGS. 13A-B are flowcharts of a method 1300 for deduplication of
data using LLRRM. In some embodiments, some of the steps of the
method 1300 are implemented by software or hardware. In some
embodiments, some of the steps of method 1300 are performed by the
deduplication layer 275 of the storage operating system 300 and
comprise the comparison function of the deduplication layer. The
order and number of steps of the method 1300 are for illustrative
purposes only and, in other embodiments, a different order and/or
number of steps are used.
In some embodiments, some steps (such as steps 1305 through 1320)
of the method 1300 may comprise a single-block deduplication
method, whereas other steps (such as steps 1325 through 1375) of
the method 1300 may comprise modifications of the single-block
deduplication method to use LLRRM. In other embodiments, some steps
(such as steps 1305 through 1320) of the method 1300 may comprise
other deduplication methods. In some embodiments, the deduplication
layer 275 may comprise an external auxiliary plug-in type software
module that works with pre-existing deduplication software to
enhance functions of the deduplication software as described
herein.
The method 1300 begins when the deduplication layer 275 receives
(at 1305) a series of blocks for processing to determine whether
any of the received blocks may be deduplicated. The received blocks
may be contained in a file (for file-based requests) or not
contained in a file (for block-based requests). A received block in
the series is set (at 1310) as a current received block. The
deduplication layer 275 then determines (at 1315) a content
identifier (e.g., checksum or hash value) for the current received
block that represents the data contents of the current received
block. The deduplication layer 275 then determines (at 1320)
whether the content identifier for the current received block
matches any content identifiers 1105 in the block-comparison
mechanism (e.g., metadata structure 290). If a matching content
identifier 1105 is not found, the method 1300 continues at step
1310 where a next received block in the series is set as the
current received block.
If a matching content identifier 1105 is found in the metadata
structure 290, this indicates a matching entry 1101 has been found
that represents a matching block. As such, a matching block has
been found to exist and the current received block is considered
redundant and may be deduplicated. To deduplicate the current
received block, the deduplication layer 275 produces (at 1325) an
index to the current address location in the mapping mechanism
using the current address location to the matching block. In some
embodiments, if the matching entry 1101 contains an address
location in LLRRM 1125, this indicates the matching stored block
has been transferred to LLRRM. As such, the current address
location comprises the address location in LLRRM 1125. If the
matching entry 1101 does not contain an address location in LLRRM
1125, this indicates the matching stored block has not been
transferred to LLRRM. As such, the current address location
comprises the address location on a disk device 1120.
A pointer 1135 to the index is then produced and stored (at 1327)
in the matching entry 1101. The pointer 1135 may comprise an
address location (e.g., LBN) of the index within the mapping
mechanism. In some embodiments, for file-based access, the
deduplication layer 275 produces the index in the inode of the file
containing the current received block. In these embodiments, the
pointer 1135 comprises an address location of the index in the
inode for the file having the received block. In some embodiments,
for block-based access, the deduplication layer 275 produces the
index by producing a new mapping entry 1201 in the metadata
structure 290. In these embodiments, the pointer 1135 comprises an
address location of the index 1210 in the corresponding mapping
entry 1201 in the metadata structure 290.
As an optional step, if a de-staging layer 375 is implemented in
the storage operating system 300, the write log containing the
current received block is modified (at 1330) to reflect the
deduplication of the current received block. For example, the
modifications to the write log may include deleting the data
content and the LBN of the current received block from the write
log. As an optional step, in offline processing (where the current
received block may have already been written to a disk device), the
method 1300 deletes (at 1335) the current received block from the
disk device. In online processing (where the received block has not
yet been written to a disk device), the blocks of the current
received block is not subsequently stored to a disk device.
The method 1300 then increments (at 1340) the reference count 1130
in the matching entry 1101 and retrieves (at 1345) one or more
field values from the matching entry 1101. In some embodiments, the
retrieved values may include the address location on a disk device
1120, an address location on an LLRRM device 1125, a reference
count 1130, and/or a set of pointers 1135 to associated indexes.
The method then determines (at 1350) whether the reference count
1130 (indicating the number of associated indexes or associated
deduplicated blocks of the matching stored block) is equal to THN.
If not, the method continues at step 1310 where a next received
block in the series is set as the current received block.
If the reference count 1130 is equal to THN, the deduplication
layer 275 assigns (at 1355) a new address location (e.g., within
memory sub-range of address locations) in LLRRM for the matching
stored block and stores (at 1355) the address location in LLRRM
1125 in the matching entry. The method then transfers (at 1360) the
matching stored block to LLRRM at the new address location. In some
embodiments, the transfer is performed by copying the matching
stored block from a disk device (using the address location on a
disk device 1120) and storing to the address location in LLRRM
1125. As an optional step, the method 1300 deletes (at 1365) the
matching stored block from the disk device at the original address
location on the disk device 1120.
The method then modifies (at 1370) each associated index of the
matching block in the mapping mechanism to reflect the new address
location of the matching stored block in LLRRM. The method may do
so using the set of pointers 1135 contained in the matching entry
1101 to locate the associated indexes in the mapping mechanism. The
method then determines (at 1375) if any received blocks in the
received series remain for processing. If so, the method continues
at step 1310 where a next received block in the series is set as
the current received block. If not, the method ends.
The above method 1300 is performed for each received block. After
processing of all received blocks, any blocks that are not
deduplicated are non-deduplicated blocks that are to be stored to a
storage device 125. The non-deduplicated blocks are then processed
according to the entry function of the deduplication layer 275 to
create metadata entries for a set of zero or more non-deduplicated
blocks.
FIG. 14 is a flowchart of a method 1400 for processing the
non-deduplicated blocks to produce new metadata entries 1101 in the
block-comparison mechanism (e.g., metadata structure 290) for
possible use in deduplicating subsequently received blocks. In some
embodiments, some of the steps of the method 1400 are implemented
by software or hardware. In some embodiments, some of the steps of
method 1400 are performed by the deduplication layer 275 of the
storage operating system 300 and comprise the entry function of the
deduplication layer. The order and number of steps of the method
1400 are for illustrative purposes only and, in other embodiments,
a different order and/or number of steps are used. Note that the
non-deduplicated blocks have address locations (e.g., LBNs)
assigned by the file system layer 350 indicating where the
non-deduplicated blocks are to be stored on a storage device
125.
The method 1400 begins by determining (at 1405) a set of
non-deduplicated blocks for processing. A non-deduplicated block in
the set is set (at 1430) as a current block. The deduplication
layer 275 produces (at 1435) a content identifier (e.g., checksum
or hash value) for the current block. The deduplication layer 275
then produces (at 1440) an entry for the current block using the
produced content identifier as an index to store the entry into the
metadata structure 290.
The deduplication layer 275 then enters (at 1445) particular
metadata for the entry 1101. For example, the entry 1101 may
comprise the content identifier 1105, the address location on a
disk device 1120 (e.g., the LBN assigned to the non-deduplicated
block), and the reference count 1130 (which is initially set to
zero). The other metadata fields (e.g., address location on an
LLRRM device 1125, a set of zero or more pointers 1135) may
initially have null values and may subsequently be modified by the
deduplication layer 275. The method then determines (at 1450) if
any blocks remain in the set for processing. If so, the method
continues at step 1430 where a next block in the set of blocks is
set as the current block. If not, the method ends.
VI. Deduplication Based on Threshold Number of Sequential Blocks
Using LLRRM
Although typically LLRRM may have faster random read access times
than a disk device, LLRRM may be more costly (for a given amount of
data storage) than disk devices. Given the relatively higher cost
of LLRRM, it may be desirable to be selective in determining which
blocks should be transferred to the LLRRM and it may still be
desirable to store some matching blocks on a disk device in some
situations.
In some embodiments, the deduplication methods and apparatus using
LLRRM described above (referred to as the "LLRRM" method and
apparatus) are used in combination with a deduplication method and
apparatus for disk devices based on a threshold number (THN) of
sequential blocks (referred to herein as the "THN sequence" method
and apparatus), which are described in U.S. patent application Ser.
No. 12/110,122, entitled "Deduplication of Data on Disk Devices
Based on a Threshold Number of Sequential Blocks," by Kiran
Srinivasan, et al., filed herewith, and incorporated herein by
reference.
The THN sequence processing/method provides deduplication of data
on disk devices based on a predetermined threshold number (THN) of
sequential blocks, the threshold number being two or greater. In
these embodiments, deduplication may be performed by determining
whether a series of THN or more received blocks (referred to herein
as a "THN series") match (in data content) a sequence of THN or
more stored blocks (referred to herein as a "THN sequence"). In
some embodiments, a "sequence" of blocks indicates a series of
blocks stored on the same track of a disk device. Blocks of a
sequence have consecutive address locations (e.g., LBNs). If a
matching THN sequence is found to exist, the blocks in the THN
series may be deduplicated on the disk devices. Deduplication based
on a threshold number of sequential blocks may also reduce the
overall read latency of a file or set of blocks as the number of
seeks between tracks may be reduced on the disk devices.
For example, if the value of THN equals 5 and a series of 10 blocks
(numbered 0-9) is received, deduplication of the received blocks
may be performed when a THN series of 5 or more of the received
blocks match a THN sequence of 5 or more stored blocks (i.e., 5 or
more blocks stored on the same track on a disk device). Thus if the
THN series of received blocks 3-7 match a THN sequence of any 5
currently stored blocks, the THN series of received blocks 3-7 are
considered redundant and is deduplicated on the disk devices.
As described above, the THN sequence method may deduplicate a
series of THN or more received blocks, the threshold number being
two or greater. As such, the THN sequence method may not
deduplicate single received blocks or series of received blocks
under the THN value. In some embodiments, the single received
blocks and series of received blocks under the THN value having
matching stored blocks may be deduplicated using the LLRRM
deduplication methods described herein. In some embodiments, the
THN sequence method is performed first to deduplicate THN series of
received blocks using the disk devices, then the LLRRM
processing/method is performed to process any received blocks not
deduplicated by the THN sequence processing/method.
FIG. 15 is a flowchart of a method 1500 for deduplication of data
using the THN sequence method in combination with the LLRRM method.
In some embodiments, some of the steps of the method 1500 are
implemented by software or hardware. In some embodiments, some of
the steps of method 1500 are performed by the deduplication layer
275 of the storage operating system 300. The order and number of
steps of the method 1500 are for illustrative purposes only and, in
other embodiments, a different order and/or number of steps are
used.
The method 1500 begins when the deduplication layer 275 receives
(at 1505) a series of blocks for processing to determine whether
any of the received blocks may be deduplicated. The method 1500
then processes (at 1510) the received series of blocks using the
THN sequence method to deduplicate each THN series having a
matching THN sequence. The THN sequence method is described in the
U.S. patent application entitled "Deduplication of Data on Disk
Devices Based on a Threshold Number of Sequential Blocks" (for
example, in relation to FIGS. 14A-B and elsewhere throughout the
application).
The THN sequence method may deduplicate a series of THN or more
received blocks that match a sequence of THN or more stored blocks,
the threshold number being two or greater. As such, the THN
sequence method does not deduplicate single received blocks or
series of received blocks under the THN value having matching
stored blocks. The method 1500 then determines (at 1515) a set of
received non-deduplicated blocks that were not deduplicated by the
THN sequence processing/method and processes (at 1520) the set of
received non-deduplicated blocks using the LLRRM processing/method.
The LLRRM method may deduplicate each received block in the set
having a matching stored block according to some embodiments
herein. For example, the set of received non-deduplicated blocks
may comprise the series of blocks received (at step 1305) and
processed by the method 1300 of FIG. 13. The method 1500 then
ends.
While the embodiments described herein have been described with
reference to numerous specific details, one of ordinary skill in
the art will recognize that the embodiments can be embodied in
other specific forms without departing from the spirit of the
embodiments. Thus, one of ordinary skill in the art would
understand that the embodiments described herein are not to be
limited by the foregoing illustrative details, but rather are to be
defined by the appended claims.
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